Save time and reduce experimental failures

The EQE of each device was measured with monochromatic light (SM-250F, Bunkoh-Keiki). The light intensity was calibrated with a standard Si and InGaAs photodetector. The photocurrent was recorded using a lock-in amplifier (LI5640, NF) with a low-noise current amplifier (DLPCA-200, FEMTO). The lock-in frequency was 85 Hz. For measurements with a reverse bias, the DC voltage output of the current amplifier was used.

All measurements are performed in continuous wave mode in order to achieve stable operation conditions. For the integral measurements of the bias-dependent intensity plot in Fig. 2c, the samples are mounted on a probe, which is put directly in a liquid helium Dewar to efficiently cool the devices and to obtain a reproducible and stable temperature, which is important for continuous wave operation. The emitted intensity is measured using a Ga-doped Ge detector. The spectral measurements are performed using a Bruker Vertex 80 FTIR spectrometer with a resolution of 2.25 GHz. The emitted light is recorded with an attached pyroelectric deuterated triglycine sulfate detector. The sample is mounted in a liquid helium cooled flow cryostat, attached to the spectrometer.

EL spectra and quantum efficiency were measured on a REPS Pro system (Enlitech) with a Keithley 2400 external current/voltage source meter connected to support an external electric field. FTPS-EQE was recorded on a FTPS (PECT-600) system (Enlitech), where a low-noise current amplifier was employed to amplify the photocurrent generated from the photovoltaic devices with illumination light modulated by the Fourier transform infrared (FTIR) instrument.

The EQE measurements were conducted by a commercially available QE‐R system from Enlitech (with greater than ≈99.5% repeatability). A Xenon lamp was installed in the system. The light was then directed into a monochromator for single wavelength beam output. The wavelength step was set to 5 nm to obtain accurate measurements. The single wavelength light beam was directed onto the active area of the device. The illumination was modulated via a chopper (165 Hz) which was connected to a lock‐in amplifier, thereby ensuring that the device output photovoltage signal frequency was synchronized for accurate signal recording. The temperature of the measurement state was set to 25 °C using a temperature controller. The averaging sampling rate during data acquisition was set to 15, while the allowed noise range was set to 5E‐4 for precise measurements. Prior to the EQE measurement, the system was calibrated against two reference photodetectors: Si photodetector from 300 to 1100 nm (Enlitech Model RC‐S103011‐E) and Ge photodetector from 1100 to 1200 nm (Enlitech Model RC‐G108018‐E). The signal‐to‐noise ratio of the two reference photodetectors is given in Figure S17 in the Supporting Information. The EQE repeatability of separate devices is shown in Figure S5 in the Supporting Information. The IQE was calculated by the following equation
$$\mathrm{IQE}=\mathrm{EQE}/\mathrm{Absorption}$$ where the absorption results in Figure 3b were utilized. The spectral responsivity R_λ was determined by
$$R_{\lambda }=\mathrm{EQE}\times \lambda \times \frac{e}{hc}$$ where λ is the wavelength of photons, e is the elementary charge, h is Plank's constant, and c is the vacuum light speed.
Current–voltage (I–V), capacitance–voltage (C–V), and temporal response with on/off illumination were measured using a Keithley 4200 semiconductor analyzer. Diode lasers (Thorlabs) of different wavelengths (515, 780, and 980 nm) were properly aligned and focused onto the device region. The measured photocurrents by using the Keithley 4200 semiconductor analyzer (0.1 fA rated noise measurement with two remote amplifiers (4225‐RPM) for ultra‐low current measurement) also confirmed the high EQE results. The incident laser beam was calibrated by a sensitive optical power meter (Thorlabs PM200, with a S120C photodiode power sensor for power levels down to nanowatts). The photocurrents (linear region) in Figure 4d and the correspondingly calculated responsivity were consistent with the measured high EQE results as per the relationship given in Equation (4).
The photocurrent I_ph was calculated by
$$I_{\mathrm{ph}}=I_{\mathrm{light}}-I_{\mathrm{dark}}$$ where I_light is the current under illumination and I_dark is the dark current.
The specific detectivity D* was calculated by
$$D^{\ast }=\frac{R_{\lambda }\sqrt{S}}{\sqrt{2e{I}_{\mathrm{dark}}}}$$ where S is the effective area of the photodiode.
For temporal response measurements, fiber‐coupled diode lasers at 515 and 1060 nm wavelengths (Thorlabs LP515‐SF3 and Qphotonics QFBGLD‐1060‐10BTF) were mounted into laser mounts, which were connected to a laser driver (Thorlabs LDC 210C) and a temperature controller (Thorlabs TED 200C). A function generator (Hewlett Packard 33120A) was connected to the laser driver, to impress a square signal to modulate the laser frequency at 1000 Hz. The photovoltage of the devices was recorded by a digital oscilloscope (Tektronix MDO3024).

The EL measurements were performed using an Andor SR-303i-B spectrometer equipped with a silicon (Si) (DU420A-BR-DD) and an indium–gallium–arsenide (InGaAs) (DU491A-1.7) detector. Voltage was supplied by a Keithley 2400 source meter and was typically 1 V. For some low signal devices, the voltage was raised up to 3 V in order to get enough EL response. To prevent device heating when the EL signal was measured in the near-IR, the voltage was pulsed for 90 s. The voltage used was the same throughout the entire spectrum (for the silicon and germanium detectors) and then the final continuous EL spectrum was obtained, after subtraction of the dark background signal.

Spectra of the sample are recorded using a Bruker Vertex 80 FTIR spectrometer with a resolution of 2.25 GHz, using an pyroelectric deuterated triglycine sulfate (DTGS) detector. The device is mounted in a liquid-helium-cooled-flow cryostat that is optically coupled to the spectrometer via parabolic mirrors. For L–I–V measurements, the light intensity L is acquired by feeding the FTIR-detector output (internal DTGS detector) into a lock-in amplifier (Stanford Research Systems SR830) and measuring the signal at the modulation frequency of 10 Hz. The current flowing through the device is measured with a coaxial current probe (Tektronix CT-1), which is connected to the output of a voltage pulser (HP8114A). The measurement data of the current I and voltage V are acquired using a digital oscilloscope (Tektronix DPO 3032).

Highly sensitive EQE was measured using a integrated system (PECT-600, Enlitech), where the photocurrent was amplified and modulated by a lock-in instrument. EQE_EL measurements were performed by applying external voltage/current sources through the devices (ELCT-3010, Enlitech). All of the devices were prepared for EQE_EL measurements according to the optimal device fabrication conditions. EQE_EL measurements were carried out from 0 to 2 V).

EQE_EL values were obtained from an in-house-built system including a Hamamatsu silicon photodiode 1010B, a Keithley 2400 SourceMeter to provide voltage and record injected current, and a Keithley 485 Picoammeter to measure the emitted light intensity.

Devices are fabricated as outlined in the device fabrication part. FTPS-EQE measurements were carried out using a Vertex 70 from Bruker optics, equipped with QTH lamp, quartz beam splitter and external detector option. A low noise current amplifier (DLPCA-200) was used to amplify the photocurrent produced upon illumination of the photovoltaic devices with light modulated by the FTIR. The output voltage of the current amplifier was fed back to the external detector port of the FTIR, in order to use the FTIR's software to collect the photocurrent spectrum.

Highly sensitive EQE was measured using an integrated system (PECT-600, Enlitech), where the photocurrent was amplified and modulated by a lock-in instrument. EQE_EL measurements were performed by applying external voltage/current sources through the devices (ELCT-3010, Enlitech).

Highly sensitive EQE was measured using an integrated system (PECT-600, Enlitech), where the photocurrent was amplified and modulated by a lock-in instrument. EQE_EL measurements were performed by applying external voltage/current sources through the devices (ELCT-3010, Enlitech).

FTIR spectra were taken on an IFS-66V/S FTIR spectrophotometer. TEM and HRTEM images were obtained measured on a JEM-2100F transmission electron microscope. XPS measurements were performed on an ESCALAB250 spectrometer. UV-vis absorption spectra were measured on a UV-2600 (Shimadzu) spectrophotometer, and PL spectra on a FLS920P fluorescence spectrometer. Absolute PL QYs were measured on an Edinburgh FLS820-s spectrometer with a calibrated integrated sphere. 1H NMR spectra were obtained at room temperature on a Zhongke Niujin AS400 (400 MHz, 1H) instrument. TRPL measurements were conducted on a time-dependent single photon counting system based on the FLS920P Edinburgh spectrometer with an excitation wavelength of 365 nm. TA spectra were measured using a femtosecond transient absorption pump-probe spectrometer (Ultrafast Systems LLC) with a pump wavelength of 365 nm. XRD patterns were obtained on a Bruker D8 Advance X diffractometer with Cu K_α Source (λ = 1.5406 Å). SEM images were collected on a Hitachi SU8000 SEM (Hitachi Limited, Tokyo, Japan) under 5 kV acceleration voltage. UPS measurements were performed on a PREVAC system. LED performance was evaluated using the commercially available system (SHENZHEN PYNECT SCIENCE AND TECHNOLOGY Co, Ltd.), with current density-voltage characteristics been recorded on a Keithley 2400 source meter, and light-output measurements on a fiber integration sphere coupled with a QE Pro spectrometer.

The current density-voltage and photon count intensity-voltage characteristics of the devices were measured by using a Keithley 2400 (Keithley instruments Inc.) and FLS920 (Edinburgh Instrument). The absorption spectra was measured in the wavelength range of 300–900 nm with a UV-vis spectrophotometer (U-3310 UV-vis HITACHI). The decay kinetics was measured by FLS920. All measurements were done at room temperature under ambient air.

To perform FI-ESR measurements, a transistor was attached and wire-bonded to a substrate holder with source, drain, and gate connections. The device-and-boat combination was lowered into a tube appropriate for ESR measurements and sealed under nitrogen using a rubber cap. The electrode wires were punctured through the cap in order to connect to the voltage source, and the puncture sites were sealed with epoxy to preserve vacuum.
All EPR measurements were taken on a Bruker E500 spectrometer using a Bruker ER 4122SHQE cavity and an X-band microwave source. An Oxford Instruments ESR900 cryostat controlled by an Oxford Instruments Mercury iTC was used for temperature-dependent spectra, and a Keithley 2602b source unit was used for electrical characterization. CustomXepr, a Python package developed by ref. ^{18 (link)}, was used to integrate data collected by these instruments and to automate measurements when desired.

DC ELQE was measured by a calibrated silicon photodiode (Thorlabs, FDS10X10), which was directly attached to the device. Two separate source measure units (SMUs) were used for applying voltage to the device and reading photocurrent from the photodiode, respectively. For AC measurement, a pulse generator (HP 8114A) applied voltage pulses (2 Hz, 500 ns duration) with a load resistance (R_L) of 47 Ω. EL was measured using a biased Si photodiode (Thorlabs, DET100A2, rise time of 35 ns), connected to a current amplifier (FEMTO, DHPCA‐100) with a set gain of 10³ V A⁻¹ and bandwidth of 200 MHz. Considering a limited diameter of photodiode (9.8 mm) and its distance to the emissive device (4.4 mm), a correction factor was applied to the measured EL flux (assuming Lambertian emission). Voltages applied to before and after R_L (V₁ and V₂, respectively) and output of the current amplifier were read by an oscilloscope (Rohde&Schwarz HMO3004). To avoid the permanent damage to the device, the measurement with a photodiode was performed over the limited V₂ range of 0–30 V. Then, the device was moved to the spectrometer setup and V₂ was swept over 0–40 V (V₁ of 0–70 V). EL spectrum was measured at each voltage using a spectrometer equipped with an array of cooled charge‐coupled devices (CCDs), with a long integration time of 20 s to compensate the low duty cycle of the pulse. The photon flux at V₂ > 30 V was plotted using the area of EL spectrum, which was calibrated with the data using a photodiode at the same condition. The SMUs and oscilloscope were controlled with the software SweepMe! (sweep‐me.net).