Efficient Inverted Perovskite Solar Cells with a Low‐Dimensional Halide/Perovskite Heterostructure

Abstract

The photovoltaic performance of inverted (positive‐intrinsic‐negative) perovskite solar cells (PSCs) is predominantly limited by interfacial recombination loss. Here, by constructing a low‐dimensional halide/perovskite heterostructure, non‐radiative recombination pathways at the perovskite/C60 contact are effectively eliminated and a voltage loss of only 370 mV is achieved in inverted PSCs. Through molecular engineering of the organic spacer, a strong electronic coupling is enabled at the heterointerface, which effectively shifts the gap states out of the bandgap and leads to a prolonged carrier lifetime of 4.28 µs. Our strategy enables a power conversion efficiency of 24.09% (certified 23.54%) for inverted PSCs with an open‐circuit voltage of 1204 mV, and an efficiency of 21.89% (certified 21.48%) for centimeter‐scale cells. The devices retain 92% of the initial efficiency after 85 °C thermal aging for over 1400 h, and 95% of the initial efficiency after 1008 h of maximum power point operation under AM1.5G illumination in air.

Synergetic Excess PbI2 and Reduced Pb Leakage Management Strategy for 24.28% Efficient, Stable and Eco‐Friendly Perovskite Solar Cells

“…As depicted in Figure S2 (Supporting Information), the EMIM + cation in [EMIM]TOS could specially form the ultra-stable supramolecule or 1D perovskite structure with PbI 2 , holding the promise to simultaneously remove the residual PbI 2 in the perovskite layer and achieve stable devices. [28,[34][35][36][37][38] In addition, the SO 3 − of TOS − also can realize excellent interfacial properties through coordination reaction with SnO 2 ETL. [39][40][41][42] First, the density functional theory (DFT) calculation was conducted to understand the interaction way between TOS − and SnO 2 in our case.…”

Bifunctional Hole-Transport Materials with Modification and Passivation Effect for High-Performance Inverted Perovskite Solar Cells

“…The methods to improve the efficiency of PSC devices include controlling perovskite crystal growth, interface modification, and innovative optimization of charge transport layers. − The traditional HTM used in p – i – n devices is PTAA. However, PTAA as a polymer, its complex synthesis process and purification process, leading to the expensive price, and the poor synthesis repeatability also seriously restrict the device commercialization. , It is reported that the organic small-molecule HTMs can not only transport holes but can also form self-assembled monolayers on ITO or passivate the perovskites to significantly reduce nonradiative recombination, generating a PCE of the inverted device as high as 25.4%. − Therefore, organic small-molecule HTMs are ideal candidates due to their simple synthesis, clear structure, and ability to further interact with ITO or perovskite through specific element groups, which can passivate the interface contact and reduce radiative recombination. − However, organic small-molecule HTMs that can interact with both ITO and perovskite in inverted PSCs are rarely reported.…”

Transfer-Imprinting-Assisted Growth of 2D/3D Perovskite Heterojunction for Efficient and Stable Flexible Inverted Perovskite Solar Cells

“…12,13 The surface treatment is especially important for the inverted PSCs because the nonradiative recombination at the perovskite/CTLs interface is the underlying cause for their inferior performance to the regular PSCs. 14,15 Among the various strategies for the surface treatment, forming 2D/3D perovskite heterojunctions by inserting the 2D perovskites at the interface has attracted much attention. 16,17 The moisture permeation and ion migration that easily occur in 3D perovskites can be effectively prevented by the organic spacer cations in the 2D perovskites.…”

“…23,24 A clear junction is favorable for shaping the optimal electrical field, while a 2D perovskite with nonuniformity or uncontinuity of the film is prone to be formed by the solution processes due to the penetration of the cation into the underlying polycrystal perovskites. 14,25 Moreover, orientation of the domains in the perovskite films is favorable for charge transport compared to that with random orientation, while the solution process often leads to random crystalline orientation. 26,27 Recently, a solidphase process was reported to generate the 2D/3D bilayer, while the 2D film grown from the stacked solid 2D precursor is prone to be thick and unfavorable for the carrier transport.…”

“…Perovskite solar cells (PSCs) have accumulated considerable research efforts, and the power conversion efficiency (PCE) has dramatically increased to 26%. − Despite the rapid progress of the PCE, however, long-term stability is a major bottleneck limiting their commercialization. , Their instability can be ascribed to intrinsic instability of the 3D perovskites and defects at the perovskite surface as well as ion migration between the 3D perovskites and carrier transport layers (CTLs). Especially, the density of the surface defects is 2 orders of magnitude higher than that within the bulk perovskite films. , Therefore, the surface treatment of the perovskite films to passivate surface defects and suppress ion migration is vital for high-efficiency and stable planar PSCs. , The surface treatment is especially important for the inverted PSCs because the nonradiative recombination at the perovskite/CTLs interface is the underlying cause for their inferior performance to the regular PSCs. , Among the various strategies for the surface treatment, forming 2D/3D perovskite heterojunctions by inserting the 2D perovskites at the interface has attracted much attention. , The moisture permeation and ion migration that easily occur in 3D perovskites can be effectively prevented by the organic spacer cations in the 2D perovskites. , Meanwhile, the nonradiative charge recombination of the 3D bulk perovskites can be suppressed by defect passivation induced by the 2D perovskites . Therefore, the inverted PSCs with exceptional performance are expected by employing 2D/3D perovskite heterojunctions.…”