Inorganic–organic
hybrid perovskite solar cells (PSCs) typically
embrace Sn-doped In2O3 (ITO) and F-doped SnO2 (FTO) as transparent electrodes, which are rigid and brittle,
retarding the commercialization of flexible PSCs (FPSCs). Here, we
fabricated flexible amorphous transparent V-doped In–Zn–O
(IZVO) thin films with varied concentrations of V atoms at room temperature.
The impacts of V concentration on the chemical, electrical, and optical
properties of IZVO thin films were thoroughly investigated. The incorporation
of V into IZO was demonstrated to suppress the formation of oxygen
vacancies and thus reduce the carrier concentration in IZO. The IZVO
thin film affords the best electrode performance with an optimum V
concentration of 0.46 atom %. In contrast to the conventional ITO
transparent electrodes that require a high processing temperature,
the amorphous transparent IZVO electrode deposited at a low temperature
without any heating and postannealing process showed a low sheet resistance
(∼22.6 Ω/□), high conductivity (∼2210 S/cm),
high optical transmittance (∼88.8%), and in particular, excellent
mechanical flexibility and fatigue robustness. Therefore, the amorphous
transparent IZVO electrode-based perovskite solar cells (PSCs) showed
superior performance (14.57%) compared to the amorphous ITO electrode-based
PSCs (11.96%), due to the significantly improved short-circuit current
density (J
SC), open-circuit voltage (V
OC), and fill factor (FF). Moreover, the IZVO
electrode-based FPSC device retained 77% of its initial power conversion
efficiency (PCE) after 100 bending cycles, while the PCE of the amorphous
ITO electrode-based FPSC dropped by 80% after only 30 bending cycles.
Combining the excellent mechanical flexibility and fatigue robustness,
the flexible amorphous IZVO electrode shows great potential for highly
efficient flexible photovoltaic applications.
The
optimal choice of electron transporting materials is of vital
importance in improving the efficiency and reducing the cost of perovskite
solar cells (PSCs) as electron transport layers (ETLs) play a key
role in charge extraction and transfer. Despite SnO2 being
a commonly used ETL, magnetron-sputtered SnO2 continues
to be constrained by oxygen vacancy (VO)-related point
defects, which result in severe interface charge recombination, thereby
limiting the open-circuit voltage and fill factor of PSCs using magnetron-sputtered
SnO2 ETLs. Herein, a doping strategy was adopted to suppress
the defect density in magnetron-sputtered SnO2, in which
Mg:SnO2 (MTO) was prepared by magnetron co-sputtering of
MgO and SnO2 at room temperature. After Mg doping, the
VO defects were passivated, the density of the trap states
in the SnO2 ETL was reduced, and the energy level alignment
between the ETL and perovskite layer was optimized. As a result, the
undesired charge recombination was effectively suppressed, thus leading
to an approximately 8.7% increase in the average device efficiency
and approximately 11% increase in the stabilized power output. The
best-performing device achieved an efficiency of 19.55%, therefore
indicating the high potential of the magnetron-sputtered Mg:SnO2 ETL toward the commercialization of PSCs.
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