Unveiling the Low‐Temperature Pseudodegradation of Photovoltaic Performance in Planar Perovskite Solar Cell by Optoelectronic Observation

Abstract

The time evolution of the current–voltage characteristic of planar heterojunction perovskite solar cell (PSC) is studied within an operating temperature range of 200–325 K. The photovoltaic (PV) performance of PSC is found to be influenced by five carrier transport pathways, which strongly depend on operating temperature and light illumination. At low temperature, a severe degradation of PV performance is presented but temporary. This is attributed to ion accumulation at the TiO2/CH3NH3PbI3 and hole transport material/CH3NH3PbI3 interfacial regions, as an origin of screening effect of built‐in field, evidenced by the low external quantum efficiency (EQE). By light illumination at open‐circuit, a steady PV performance will be reached and the stabilization time increases with decreasing temperature. The recovery of PV performance is attributed to ion diffusion in CH3NH3PbI3 layer in the absence of electric field. The EQE observations indicate that photogenerated carriers are separated and collected efficiently after a long time light illumination due to a reduction of the screening effect. At high temperature, because of the low ion density at interfacial regions, the PV performance shows a quick response to light. These findings may help understanding of the mechanism of temperature‐dependent photogenerated carrier transport in the PSC.

Migration of cations induces reversible performance losses over day/night cycling in perovskite solar cells

“…[25][26][27] Several studies indicated that, regardless of particular architecture and constituents within the PSCs, X defects migrate and reversibly accumulate within the perovskite lattice in narrow Debye layers at the interfaces with the charge selective contacts. 19,[28][29][30][31][32][33][34] Depending on voltage and light bias conditioning, accumulation of ions (and their vacancies) partially screens the built-in electric field and possibly creates interfacial electronic trap states, which reduce the charge extraction efficiency. 25,30,31,[34][35][36][37][38][39][40][41][42][43] Ion migration on timescales from 10 -1 to 10 2 s has been widely investigated to explain the hysteresis of current density-voltage (J-V) curves.…”

“…prolonged exposure to continuous light and voltage bias. 29,39,[50][51][52][53][54][55] In this work, we provide direct evidence of electric field-induced ion migration and its effects on the long-term performance of perovskite solar cells working under different loads.…”

Low-Temperature Induced Enhancement of Photoelectric Performance in Semiconducting Nanomaterials

“…There are a handful of reports showing decreased performance at low temperature. These weakening phenomena caused by lowering temperature are ascribed to many causes including frozen carrier diffusion [ 13 ], reduced absorption [ 14 ], interfacial ion accumulation [ 15 ], phase transition [ 16 ] and radiative [ 17 ] and nonradiative [ 18 ] recombination. However, there are also many reports that low-temperature operation is not a restriction but an enhancement to overall photoelectric performance, ranging from low-dimension materials to nanocrystals.…”

Unusual Bimodal Photovoltaic Performance of Perovskite Solar Cells at Real-World Operating Temperatures

“…However, few studies have dealt with the temperature and light intensity dependence separately. Many of the previous reports have primarily emphasized the impact on PSC performance at low temperatures and in phase transition regions, and those studies have been conducted on relatively unstable perovskite compositions (e.g., CH 3 NH 3 PbI 3 , or MAPbI 3 for short), while other relevant compositions are yet to be investigated in depth. ,, Moreover, theories about the mechanisms that drive PCE variations are still inadequate and open to debate.…”

“…In most conventional solar cell semiconductors, such as silicon, CIGS, and CdTe, the PV performance declines with increasing temperature, resulting in a negative temperature coefficient (TC) throughout the operating temperature range. , Temperature-dependence studies of PSCs based on MAPbI 3 absorbers reported a monotonic decrease in PCE and other PV parameters (i.e., open-circuit voltage ( V oc ), short-circuit current density ( J sc ), and fill factor (FF)) when the temperature was increased above RT . The degradation of organic-compound-based hole/electron transport materials, such as Spiro-OMeOTAD and Phenyl-C61-butyric acid methyl ester (PCBM), by pinhole formation and halide migration into the charge transport layers is reported as one of the main factors behind this decline. ,,,, A pseudo-degradation of PV performance and a slow photoresponse have been reported at low temperatures and attributed to charge accumulation at the transport layer/perovskite interface . Studies of MAPbI 3 over a wide range of temperature (−40 to 100 °C) have generally shown a significant decrease in performance at low and high temperatures, with a maximum PCE in the range 20–40 °C. , However, other studies have observed a steady improvement in PCE when the temperature was decreased from 25 to −20 °C .…”