Bishal Bhandari

In solar cell research, transparent conducting electrodes (TCEs) are typically not included in device optimization. In this study, we investigate the properties of TCEs to identify the most important one(s) for the performance of large-area perovskite solar cells (PSCs), which is vital for advancing their commercial viability. By keeping the absorber and the PSC device structure constant, we pinpoint the TCE conductivity as the critical factor. We then design a hybrid TCE, composed of silver nanowires (AgNWs) and indium zinc oxide layers on a polyethylene terephthalate substrate, which has a sheet resistance ( R _□ ) lower by a factor of 2 (∼5.7 vs. 9.8 Ω □ ⁻¹ ), with only a minor trade-off in average transmittance and surface roughness. PSCs with a 1.4 cm ² device size fabricated on the lower- R _□ hybrid TCE have enhanced PSC performance due to improved fill factor (FF). Furthermore, we show that the FF and power conversion efficiency of the 1.4 cm ² area PSCs decrease with increasing series resistance, which is not observed for the 0.1 cm ² area PSCs. Finally, technology computer-aided design simulations further confirm the experimental results and indicate that the TCE R _□ must be below 10 Ω □ ⁻¹ to achieve good performance in large-area devices. These findings highlight the importance of TCE design for specific applications and that AgNW-based TCEs offer an effective pathway to improving the performance of large-area PSCs.

This study investigates how the performance of perovskite solar cells (PSCs) made on polyethylene terephthalate (PET) substrates depends on transparent conducting electrodes (TCEs) and hole transport layers (HTLs). We fabricated PSCs using commercially available PET/TCEs and compared their performance with PSCs manufactured on Glass/indium tin oxide (ITO) substrates. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) with varying levels of acidity and NiO nanoparticles were used as HTLs. The current density-voltage characteristics of PSCs made on PET/TCEs were found to be significantly lower when highly acidic PEDOT:PSS was used as the HTL. However, this was not observed for PSCs made on Glass/ITO. To investigate the interaction between HTL and TCE, atomic force microscopy was carried out after dipping the TCEs in PEDOT:PSS solutions of different acidity. X-ray photoelectron spectroscopy measurements further revealed differences in the chemical composition between ITO film on PET vs. on glass. Our results indicate that the performance of PSCs depends both on the TCE substrates and HTLs, which can be explained by their chemical interaction.

Optimizing the spin coating of silver nanowires to form transparent conducting electrodes (TCE) is guided by machine learning (ML). A good TCE has two competing characteristics: high transmittance and high conductance. Optimization using a scalar figure of merit, as often done in the field, cannot satisfy the independent requirements for transmittance and conductance imposed by specific applications. By performing a Pareto front analysis based on ML models, we show that the desired outcomes of transmittance >= 75% and sheet resistance <= 15 omega/sq are challenging but can be achieved using processing parameters identified by ML analysis.