Band Alignment Strategy for Printable Triple Mesoscopic Perovskite Solar Cells with Enhanced Photovoltage

Abstract

Printable triple mesoscopic structures for organic–inorganic hybrid perovskite solar cells (PSCs) have recently obtained significant attention, and they possess a superior long-term stability in comparison to those of planar structured PSCs. In comparison with planar structures, however, triple mesoscopic structures typically show lower open-circuit voltages (V oc). Evidence suggests that nonradiative recombination governed by the mismatched energy levels between the perovskite film and the electron-transporting layer (or hole-transporting layer) is the main cause for photovoltage losses. Here we introduced a gradient bilayered zinc tin oxide (ZTO) ETL for fully printed mesoporous PSCs. This approach reduces the energy loss and augments the V oc, which benefits from the suitable matching of cascade level between the perovskite and the ZTO ETL. By tuning of the Zn content, ZTO films with gradient energy levels and different carrier concentrations are acquired. Our optimized device delivers a high V oc of 1.02 V and PCE of 15.86%. These findings provide a simple pathway to design the interface between ETL and perovskite and to tailor the band alignment to suppress interfacial trap-assisted recombination of fully printed mesoporous PSCs for enhancing V oc and charge extraction simultaneously.

A Review on Additives for Halide Perovskite Solar Cells

“…As a result, the pore was well filled and the efficiency of such printable hole‐conductor‐free PSCs was boosted to a certified efficiency of 12.84% in 2014 . This method also has been reported by several other groups . In addition to 5‐AVA, other additives which can bind to substrates and perovskites at the same time such as 4‐(aminomethyl) benzoic acid hydroiodide (ABI), butylphosphonic acid 4‐ammonium (4‐ABPA) chloride, and amino‐propyltrimethoxysilane …”

Interfacial Post‐Treatment for Enhancing the Performance of Printable Carbon‐Based Perovskite Solar Cells

“…Alternatively, interface modification and band alignment adjustment are also demonstrated to be efficient methods to reduce nonradiative recombination losses of interfaces. For example, a gradient bi‐layered zinc tin oxide electron transporting layer (ETL) was designed to reduce the energy loss and augments the open‐circuit voltage to be 1.02 from 0.92 V . The work function of carbon electrode was tuned by oxygen content in carbon or boron‐doping to improve hole extraction .…”

“…Combining the XPS analysis of the perovskite surface and EDS analysis of the perovskite bulk layer, it can be concluded that a gradient of Cs + ion concentration was formed in the perovskite layer from surface to bottom. The formed graded cation perovskite layer may form gradient band energy alignment to effectively reduce recombination at the perovskite/carbon interface …”

Dithieno[3,2‐b:2′,3′‐d]pyrrole Cored p‐Type Semiconductors Enabling 20 % Efficiency Dopant‐Free Perovskite Solar Cells

“…Thec orresponding device parameters are summarized in Table 1. [16] On the other hand, the molecular packing can be greatly affected by the substituted alkyl chains. Since control devices using doped spiro-OMeTAD also show similar hysteresis,the origin of J-V hysteresis can be ascribed to the perovskite itself including trap states,ion migration, or interface problems such as imbalance of charge transport.…”

“…HOMO energy level in films), resulting in am ore matched interfacial band alignment with perovskite layer to increase the V OC of PVSCs. [16] On the other hand, the molecular packing can be greatly affected by the substituted alkyl chains. In our case,the longer branched alkyl chain lead to asmoother film surface and higher hole mobility.A ss uch, the proof-of…”