Constructing Chromium Multioxide Hole‐Selective Heterojunction for High‐Performance Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) suffer from significant nonradiative recombination at perovskite/charge transport layer heterojunction, seriously limiting their power conversion efficiencies. Herein, solution-processed chromium multioxide (CrO x ) is judiciously selected to construct a MAPbI 3 /CrO x /Spiro-OMeTAD hole-selective heterojunction. It is demonstrated that the inserted CrO x not only effectively reduces defect sites via redox shuttle at perovskite contact, but also decreases valence band maximum (VBM)-HOMO offset between perovskite and Spiro-OMeTAD. This will diminish thermionic losses for collecting holes and thus promote charge transport across the heterojunction, suppressing both defect-assisted recombination and interface carrier recombination. As a result, a remarkable improvement of 21.21% efficiency with excellent device stability is achieved compared to 18.46% of the control device, which is among the highest efficiencies for polycrystalline MAPbI 3 based n-i-p planar PSCs reported to date. These findings of this work provide new insights into novel charge-selective heterojunctions for further enhancing efficiency and stability of PSCs.

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

“…As shown in Figure 4c, compared with the perovskite thin film prepared without the PCBM charge-transport layer, the DADA-treated perovskite thin film has a PL intensity that is almost twice that of the former. The enhanced PL intensity (Figure 4c) reveals that DADA helps to suppress nonradiative recombination by eliminating defect sites on the perovskite thin-film surface, 42 which is consistent with the longer carrier lifetime for the DADA-treated perovskite thin film compared to the control perovskite thin film, according to the TRPL spectra in Figure 4d. The PL attenuation curve was fitted using the following double exponential function (eq 1), 44 and the fitted results are listed in Table S1.…”

“…The UV−vis absorption spectra of the MAPbI 3 and MAPbI 3 /DADA thin films are shown in Figure 3f. Owing to both the improved perovskite thin-film crystallization and fewer interfacial defects, 42 the optical absorbance of the MAPbI 3 /DADA thin film was slightly enhanced. The Tauc diagram (Figure S7) revealed that DADA did not change the bandgap of the film (1.58 eV).…”

Synchronous Modulation of Defects and Buried Interfaces for Highly Efficient Inverted Perovskite Solar Cells

“…, [37][38] the calculated hole transfer efficiency (η t ) between the perovskite and PTAA:F4TCNQ largely increases from 53.04% to 91.4% at the PTAA:F4TCNQ/DA/perovskite:DA heterojunction.…”

“…[ 35–36 ] Moreover, the photoluminescence quantum yields (PLQYs) for the perovskite, DA/perovskite, and DA/perovskite:DA are 1.15%, 3.88%, and 6.98%, respectively, and the PLQYs of the corresponding films with PTAA:F4TCNQ are 0.54%, 0.40% and 0.60%, respectively. According to the equation: $${\eta _t} = \left( {1 - \frac{{PLQ{Y_{PVK/HTL}}}}{{PLQ{Y_{PVK}}}}} \right)$$, [ 37–38 ] the calculated hole transfer efficiency (η t ) between the perovskite and PTAA:F4TCNQ largely increases from 53.04% to 91.4% at the PTAA:F4TCNQ/DA/perovskite:DA heterojunction.…”

The degradation of perovskite precursor

“…Nowadays, almost all efforts focus on improving the power conversion efficiency (PCE) and the stability of mixedcation PSCs, e.g. additive engineering [23,24] , crystallization engineering [25,26] , component engineering [27] , interface engineering [28,29] , film-making technique [30,31] , passivation [32−34] , tandem cells [35−38] , large-area fabrication [39−41] , and flexible devices [42,43] . The precursor ageing issue does not receive enough attention.…”