Effect of passivation on buried interface of CsPbI2Br perovskite films

Abstract

Passivation on the surface or interface is one of the key issues in fabricating the efficient and stable perovskite solar cells (PSCs). In this Letter, we report a way to passivate the buried interface on the perovskite film by optimizing the growth kinetics of the precursor film. A solvent-controlled growth (SCG) strategy of the precursor film is adopted, that is, inducing the solvent volatilization of the precursor film before high-temperature annealing. It is found that the solvent distribution of the precursor film is the key to the growth kinetics of perovskite films. The vacuum pretreated precursor film can obtain a dense buried interface to avoid the generation of small grains and pores at the interfaces of the perovskite/electron transport layer after high temperature crystallization. After passivation, non-radiative recombination in CsPbI2Br films is suppressed, accompanied by favorable carrier separation and extraction at the interface. The power conversion efficiency of all-inorganic CsPbI2Br carbon-based PSCs without a hole transport layer reaches 13.46%. The SCG strategy on the precursor films provides a way to passivate the buried interface of PSCs.

Passivation Effect of CsPbBr3 Films Based on SnBr4 Post-Treatment

“…However, the intensity has significantly increased in modified samples, indicating the inhibition of nonradiative recombination. These findings are consistent with previous research. − The carrier lifetime can be derived from the decay curves of photoluminescence intensity using a biexponential decay equation: I ( t ) = I 0 + A 1 exp­(− t /τ 1 ) + A 2 exp­(− t /τ 2 ), where τ 1 and τ 2 correspond to fast decay time constants and slow decay time constants, respectively. , The average carrier lifetime (τ avg ) can be calculated as τ avg = (A 1 τ 1 2 + A 2 τ 2 2 )/(A 1 τ 1 + A 2 τ 2 ). For the TRPL measurements, the PL lifetimes of modified perovskite films are consistently longer than those of the control sample (Table ).…”

“…In the magnified [110] pesks in Figure b, it is found that the diffraction peaks shift to small angles as the concentration of SnBr 4 increases, which indicates that part of Sn 4+ has entered the lattice gap of CsPbBr 3 , causing the crystal lattice to expand Figure c displays the transmission spectra of the samples, while absorption spectra are calculated by applying the Beer–Lambert Law: A = −log T . , The fitted band gaps are shown in Figure d, and the energy bands of all samples are approximately 2.35 eV. Spectroscopic experiments have demonstrated that the post-treatment does not affect the absorption properties of the CsPbBr 3 films.…”

“…To determine the elemental composition and chemical environment of the CsPbBr 3 films, XPS measurements are performed. , The bonding energy of Sn 3d on the surface has been found to be 386 eV as shown in Figure b, corresponding to Sn 4+ . From the XPS spectra of the CsPbBr 3 films in Figure , there is a slight shift of the Br peak positions to higher binding energy when SnBr 4 is introduced into the perovskite.…”

“…41−43 The carrier lifetime can be derived from the decay curves of photoluminescence intensity using a biexponential decay equation: I(t) = I 0 + A 1 exp(−t/τ 1 ) + A 2 exp(−t/τ 2 ), where τ 1 and τ 2 correspond to fast decay time constants and slow decay time constants, respectively. 23,29 The average carrier lifetime (τ avg ) can be calculated as…”

“…In solar cells, favorable interface properties are crucial for achieving a high performance. The performance of PSCs is mainly affected by two factors: nonradiative recombination activated by surface defects and the carrier extraction determined by the energy level arrangement. − In order to reduce the defects of CsPbBr 3 films, various preparation and passivation methods have been developed. For example, methods such as continuous spin-coating, immersion, and infiltration spin-coating have been sequentially developed to obtain CsPbBr 3 films with pure phases and to minimize the effect of impurity phases on the optoelectronic properties. ,, Additive engineering using NH 4 SCN, SnBr 2 , BiBr 3 , acetic acid, 2-Guanidinoacetic acid, a light soaking-assisted method, and a solvent-controlled growth strategy have been developed to efficiently passivate defects by regulating crystallization kinetics. − Inorganic PSCs without a hole transport layer often experience significant energy level mismatches.…”