Use of Sodium Diethyldithiocarbamate to Enhance the Open‐Circuit Voltage of CH₃NH₃PbI₃ Perovskite Solar Cells

Abstract

The incorporation of additives to modulate the properties of metal halide perovskite thin films has become a successful approach in improving the power conversion efficiency of perovskite‐based solar cells. Herein, the beneficial use of sodium diethyldithiocarbamate (NaDEDTC) as processing agent in improving the open‐circuit voltage of methylammonium lead triiodide perovskite solar cells is reported. DEDTC reduces the rate of perovskite crystallization. Absorption and emission spectra show that the optical bandgap of the perovskite films remain essentially unchanged and X‐ray diffraction reveals the formation of preferentially oriented crystallites independent of the use of DEDTC. The use of DEDTC, however, results in a decrease in nonradiative decay as inferred from a two order of magnitude increase in electroluminescence efficiency, explaining the increased open‐circuit voltage. Fourier‐transform infrared spectroscopy, nuclear magnetic resonance, and X‐ray photoelectron spectroscopy show that the DEDTC ligand is not present after the film processing. Therefore, DEDTC modulates film formation but is not incorporated in the perovskite or present as a surface ligand. Sodium ions, on the contrary, are incorporated in the perovskite layer.

Pre‐buried Interface Strategy for Stable Inverted Perovskite Solar Cells Based on Ordered Nucleation Crystallization

“…Compared the results of AAD with PbI 2 -AAD, it is found that the missing hydrogen atoms and the 1 H resonance signal shifting to high frequency are due to the formation of Pb-O coordination bond and N-H…N hydrogen bond after annealing at 100 °C. [39,41] These can also be corroborated by the XPS and FT-IR measurements. From the XPS measurements (Figure 2g; Figure S7, Supporting Information), the binding energies for Pb 4f and O 1s si-multaneously upshift 0.1 eV.…”

Phase‐Stable Wide‐Bandgap Perovskites for Four‐Terminal Perovskite/Silicon Tandem Solar Cells with Over 30% Efficiency

“…The most representative band of ADDC corresponds to the CS stretching at 985 cm −1 . [ 31 ] In addition, some other characteristic bands such as CS stretching (≈1100 cm −1 ) are useful. [ 32 ] In Figure S11 (Supporting Information), only marginal differences were observed between the IR wavenumbers of the control films and the films with different concentrations of ADDC.…”

Synergistic Surface Defect Passivation of Ionic Liquids for Efficient and Stable MAPbI3-Based Inverted Perovskite Solar Cells

“…The Pb 4f peaks shifted from 137.5 eV (4f 7/2 ) and 142.3 eV (4f 5/2 ) to 138.2 and 143.1 eV for the control and DADA-treated perovskite thin films, respectively. The binding energy of Pb core levels in perovskite film increased, implying greater binding of anions and cations on the perovskite surface, which might be induced by strong binding between surface ions and DADA. , Figure c shows the XPS I 3d spectra of the control and DADA-treated perovskite thin films. The I 3d peaks shifted from 618.3 eV (3d 5/2 ) and 629.8 eV (3d 3/2 ) to 619.0 and 630.4 eV for the control and DADA-treated perovskite thin films, respectively.…”

“…Because of their ionic properties, which are related to organic-cation and halide vacancies and uncoordinated lead and iodine ions, perovskites contain various defects, which are often mainly concentrated at grain boundaries and on perovskite surfaces. − These defects capture charges, which generates nonradiative recombination and hysteresis and, thus, affects the device performance. − In addition, defects promote ion migration and charge accumulation in the device, which destroys the device structure and considerably reduces both the device stability and performance. − In the early development of PSCs, researchers mainly focused on the improvement of the perovskite active layer by engineering components, , optimizing fabrication processes, , engineering solvents, , and modifying interfaces by passivating defects − to reduce the defect densities of perovskite active layers. Interfacial modification is a facile and effective method for reducing the number of surface defects.…”