Intermolecular Exchange Boosts Efficiency of Air‐Stable, Carbon‐Based All‐Inorganic Planar CsPbIBr₂ Perovskite Solar Cells to Over 9%

Abstract

Among all inorganic halide perovskite photovoltaic materials, CsPbIBr2 exhibits the most balanced features in terms of bandgap and stability. However, the poor quality of solution‐processed CsPbIBr2 films impedes further optimization of cells performance. Herein, a facile intermolecular exchange strategy for CsPbIBr2 film is demonstrated, wherein an optimized methanol solution of CsI is spin‐coated on CsPbIBr2 precursor film in conventional one‐step solution route. It surprisingly produces full‐coverage and pure‐phase CsPbIBr2 films featured with average grain size of ≈0.65 µm, few grain boundaries, high crystallinity, preferable (100) orientation, stoichiometric composition along with favorable electronic structures for effective dissociation and transfer of carriers. Hence, the cost‐effective, carbon‐based all‐inorganic planar perovskite solar cells based on them, yield an optimized efficiency of 9.16% with a stabilized value of 8.46% in ambient air conditions that highlight a particularly superb open‐circuit voltage of 1.245 V, all of which represent the highest values reported in pure CsPbIBr2 based cells so far. Moreover, the optimized cell without encapsulation shows excellent long‐term stability because it can retain 90% over 60 days and 97% over 7 days of its initial efficiency, when is stored controllably in ≈45% relative humidity at 25 or 85 °C at zero humidity, respectively.

Band Alignment Engineering Towards High Efficiency Carbon‐Based Inorganic Planar CsPbIBr2 Perovskite Solar Cells

“…[22,23] Moreover,t he extra high-density grain boundaries or long-chain surfactants used to improve processing of the materials lead to inferiorP CEs. [6,14,15,[24][25][26][27][28][29][30][31][32][33] An impressive PCE of 9.16 %w as achieved for carbon-based all-inorganic PSCs with pure CsPbIBr 2 in our previousw ork. [6,14,15,[24][25][26][27][28][29][30][31][32][33] An impressive PCE of 9.16 %w as achieved for carbon-based all-inorganic PSCs with pure CsPbIBr 2 in our previousw ork.…”

“…[22] On the other hand, CsPbIBr 2 has an arrower band gap ( % 2.05 eV) than CsPbBr 3 and better stabilityt han both CsPbI 3 and CsPbI 2 Br. [24] Doping CsPbIBr 2 with Mn 2 + or Sn 2 + was shown to further boost the cell efficiency to over 11 %. [24] Doping CsPbIBr 2 with Mn 2 + or Sn 2 + was shown to further boost the cell efficiency to over 11 %.…”

“…[23,[34][35][36] In general,i nterface recombination in PSCs depends not only on interfaciald efects, but also more importantly on the interfacial bands tructure, [37,38] which is both theoretically supported and experimentally demonstrated. As ar esult,t he carbon-based, all-inorganic CsPbIBr 2 with the configuration of fluorine-doped tin oxide (FTO)/TiO 2 / CsPbIBr 2 /carbon, there is al arge energy difference between the conduction band minimums (CBMs) of the CsPbIBr 2 absorber and TiO 2 ETL, [14,24,27] which causes band mis-alignment. However,s ignificant interfacialr ecombination of chargec arriers in solar cells fabricated with this active layer,w hich is intrinsicallya ssociated with the unwanted conduction band misalignment between CsPbIBr 2 and the commonly used TiO 2 electron transport layer, has limited powerc onversion efficiency (PCE) values.…”

Anorganische CsPbX3‐Perowskit‐Solarzellen: Fortschritte und Perspektiven

“…Gleichzeitig fanden Ma et al in ihren CsPbBr 2 I-Schichten keine solche Phasentrennung. [150] Man kann aus der Kombination all dieser Untersuchungen schließen, dass es wohl sehr spezifisch von den jeweiligen Schichten und deren Herstellungsverfahren abhängt, ob eine Phasensegregation auftreten kann. Lau et al stellten Schichten durch Sprühabscheidung her und fanden ebenfalls keine Phasentrennung.…”

“…[147] Durch Abscheidung mittels Sprühpyrolyse erzielte die gleiche Arbeitsgruppe in einer späteren Studie eine sPCE von 6.3 %u nd V OC = 1.12 Vo hne Hysterese. [150],die eine moderate Hysterese fanden, eine große Hysterese.L i et al erhielt eine sPCE von 6.1 %und rfV OC = 1.20 V. [146] Liu et al verwendeten eine ungewçhnliche invertierte Zellenstruktur mit NiO als HTM und Au,a ufgedampft auf einer 4nmdünnen MoO 3Àx -Pufferschicht auf dem HaP.Dabei ist zu beachten, dass der Au/MoO 3 -Kontakt der Elektronenextraktions-Kontakt und nicht der Lochextraktions-Kontakt war, wie es normalerweise der Fall ist. [150],die eine moderate Hysterese fanden, eine große Hysterese.L i et al erhielt eine sPCE von 6.1 %und rfV OC = 1.20 V. [146] Liu et al verwendeten eine ungewçhnliche invertierte Zellenstruktur mit NiO als HTM und Au,a ufgedampft auf einer 4nmdünnen MoO 3Àx -Pufferschicht auf dem HaP.Dabei ist zu beachten, dass der Au/MoO 3 -Kontakt der Elektronenextraktions-Kontakt und nicht der Lochextraktions-Kontakt war, wie es normalerweise der Fall ist.…”