Interface Modification for Energy Levels Alignment and Charge Extraction in CsPbI$_3$ Perovskite Solar Cells

TL;DR

This study introduces a dipole molecule interface modification using TOPO to improve energy level alignment and charge extraction in CsPbI3 perovskite solar cells, resulting in enhanced efficiency and voltage.

Contribution

The paper presents a novel interface modification with TOPO molecules that significantly improves energy level alignment and charge extraction in CsPbI3 PSCs.

Findings

Achieved over 19% power conversion efficiency.

Realized a Voc of 1.2 V in CsPbI3 PSCs.

Demonstrated improved charge extraction via transient surface photovoltage studies.

Abstract

In perovskite solar cells (PSCs) energy levels alignment and charge extraction at the interfaces are the essential factors directly affecting the device performance. In this work, we present a modified interface between all-inorganic CsPbI$_3$ perovskite and its hole selective contact (Spiro-OMeTAD), realized by a dipole molecule trioctylphosphine oxide (TOPO), to align the energy levels. On a passivated perovskite film, by n-Octyl ammonium Iodide (OAI), we created an upward surface band-bending at the interface by TOPO treatment. This improved interface by the dipole molecule induces a better energy level alignment and enhances the charge extraction of holes from the perovskite layer to the hole transport material. Consequently, a Voc of 1.2 V and high-power conversion efficiency (PCE) of over 19% were achieved for inorganic CsPbI$_3$ perovskite solar cells. Further, to demonstrate the effect of the TOPO dipole molecule, we present a layer-by-layer charge extraction study by transient surface photovoltage technique (trSPV) accomplished by charge transport simulation.