Methylammonium-chloride post-treatment on perovskite surface and its correlation to photovoltaic performance in the aspect of electronic traps

Abstract

Herein, MACl post-treatment is utilized for MAPbI 3 and (Cs 0.05 FA 0.79 MA 0.16)Pb(I 0.84 Br 0.16) 3 (MA, methylammonium; FA, formamidinium). Photoluminescence of both perovskite films exhibits a peak shift to the higher emission energy as well as a slower decay of recombination by the MACl treatment, suggesting the passivation of defects in band tail states. Photovoltaic performance is further correlated with the change of deep electronic traps in the bandgap, which is characterized through capacitance analyses of solar cells. Degradation of MAPbI 3 cells by the MACl treatment is attributed to the additional deep-trap formation, and the improvement of photovoltaic parameters for triple-cation perovskites is correlated with the reduction of deep traps with trap-level shifts toward the band edge. The reactive characters of MAPbI 3 against post-treatment conditions seem to be responsible for the deep-trap formation as evidenced by the microstructural/morphological results, and consequently, the improved resistance to trap the formation of triple-cation perovskites provides viability for further performance enhancement by surface passivation.

Experimental Evidence of Chloride‐Induced Trap Passivation in Lead Halide Perovskites through Single Particle Blinking Studies

“…Likewise, Hwang et al found that Clpassivation of MAPbI 3 thin films resulted in an enhanced PL intensity and an extended PL lifetime, however, with inferior PV efficiency compared to the pristine perovskite. [13] In contrast, the same research group found an improved PV performance for Clpost-treated (Cs 0.05 FA 0.79 MA 0.16 )Pb(I 0.84 Br 0.16 ) 3 perovskite films but with a decreased PL intensity and shorter PL lifetime. [13] Hence, more direct and advanced optical techniques to quantify trap densities are required.…”

“…[13] In contrast, the same research group found an improved PV performance for Clpost-treated (Cs 0.05 FA 0.79 MA 0.16 )Pb(I 0.84 Br 0.16 ) 3 perovskite films but with a decreased PL intensity and shorter PL lifetime. [13] Hence, more direct and advanced optical techniques to quantify trap densities are required.…”

A Cu2O–CuSCN Nanocomposite as a Hole-Transport Material of Perovskite Solar Cells for Enhanced Carrier Transport and Suppressed Interfacial Degradation

“…These results indicate that the trap sites are apparently reduced on using an appropriate nanocomposite. Furthermore, the Nyquist plot for the device with a nanocomposite shows a larger semicircle compared to the CuSCN-only device (Figure (b)), yielding a higher recombination resistance, which indicates the decreased trap sites near the interface. − Additional trap distribution spectra shown in Figure (c) from the capacitance–frequency analysis indicate that defects of the nanocomposite-based device are lowered by ∼0.04 eV toward the band edge, and the trap density is also reduced compared to the CuSCN-only device. − As discussed in the Introduction, the OHP/CuSCN interface can produce impurities such as PbI 2 and CuI . Also, there are possibilities of OHP defects due to halide migration occurring frequently during the operating conditions (light, heat, and air). , Results from the trap analyses suggest that Cu 2 O can effectively suppress the formation of defects at the interface between OHP and CuSCN, thus improving charge transport and decreasing defect concentration in the device, with the schematic diagram shown in Figure (d).…”

CuCrO2 Nanoparticles Incorporated into PTAA as a Hole Transport Layer for 85 °C and Light Stabilities in Perovskite Solar Cells

“…The effect of CuCrO 2 nanoparticles on both thermal and light stabilities of the solar cells were also investigated. For thermal stability, encapsulated devices were stored under standard damp heat conditions (85 °C/85% relative humidity (RH)) [ 25 , 79 , 80 ], where encapsulation was applied to block other external degradation factors than heat. High humidity was used to detect devices with damaged encapsulation which would undergo rapid moisture-induced degradation with a leak.…”