Hybrid growth techniques combining chemical vapor deposition (CVD) and solution processing have emerged as a promising pathway to fabricate perovskite-silicon tandem solar cells. These methods leverage the advantages of both approaches to address challenges in interfacial passivation, spectral matching, and efficiency optimization. The tandem architecture capitalizes on the complementary bandgaps of perovskite and silicon to achieve higher power conversion efficiencies than single-junction devices, with recent records surpassing 33%.
CVD offers precise control over film thickness, uniformity, and conformality, making it suitable for depositing charge transport layers and perovskite top cells on textured silicon substrates. Common CVD techniques include low-pressure CVD and plasma-enhanced CVD, which enable the growth of high-quality electron and hole transport layers such as tin oxide and nickel oxide. These layers play a critical role in minimizing recombination losses at interfaces. Meanwhile, solution processing allows for the cost-effective deposition of perovskite absorbers with tunable bandgaps. Techniques like spin-coating, blade-coating, and slot-die coating are employed to form perovskite films with compositions optimized for spectral matching with the silicon bottom cell.
Interfacial passivation is a key challenge in perovskite-silicon tandems due to the sensitivity of perovskite materials to surface defects and environmental factors. CVD-grown buffer layers, such as ultrathin aluminum oxide or silicon oxide, have been shown to reduce non-radiative recombination at the perovskite-silicon interface. These layers act as chemical and electrical barriers, preventing ion migration and charge carrier trapping. Solution-processed passivation strategies, including the use of bulky organic cations or halogen-rich precursors, further enhance interface quality by filling vacancies and suppressing defect states.
Spectral matching between the top and bottom cells is critical for maximizing photon utilization. The perovskite layer is typically engineered to have a bandgap between 1.6 and 1.8 eV to complement silicon’s 1.1 eV bandgap. This is achieved through compositional tuning via solution processing, such as mixing formamidinium and cesium cations with varying halide ratios. CVD-deposited anti-reflection coatings and textured light-trapping structures improve broadband absorption across the tandem stack. Recent designs incorporate graded refractive index layers grown by CVD to minimize optical losses at the perovskite-silicon junction.
Efficiency records for perovskite-silicon tandems fabricated via hybrid methods have progressed rapidly. In 2023, a team achieved 33.7% efficiency using a combination of CVD-deposited transport layers and solution-processed perovskite. The device featured a two-terminal configuration with a monolithic interconnection layer grown by atomic layer deposition, a technique closely related to CVD. Key to this achievement was the optimization of the recombination layer between subcells, which balanced current matching while maintaining high open-circuit voltage. Other groups have reported stabilized efficiencies above 32% with similar hybrid approaches, demonstrating the reproducibility of these methods.
The thermal stability of perovskite-silicon tandems remains an area of ongoing improvement. CVD can deposit encapsulation layers such as silicon nitride at temperatures compatible with the underlying perovskite film. Solution additives like polymer networks or inorganic crosslinkers have been incorporated into the perovskite precursor to enhance thermal resilience without compromising optoelectronic properties. Accelerated aging tests show that hybrid-fabricated tandems retain over 90% of initial performance after 1000 hours under standard illumination and temperature conditions.
Scalability considerations favor the hybrid approach for industrial adoption. CVD tools are already deployed in silicon photovoltaic manufacturing lines, while solution processing enables high-throughput deposition of perovskite layers. Researchers have demonstrated tandem modules with active areas exceeding 20 cm² using slot-die coating for perovskite deposition and in-line CVD for transport layers. The compatibility with textured silicon heterojunction bottom cells, which dominate high-efficiency silicon photovoltaics, further strengthens the case for hybrid fabrication.
Economic analyses suggest that perovskite-silicon tandems made via hybrid methods could achieve levelized costs of electricity below conventional silicon modules, provided that stability targets are met. The additional manufacturing steps for the perovskite top cell are offset by the higher power output per unit area. Material costs for solution-processed perovskites remain low, with lead halide precursors constituting less than 5% of the total module cost. CVD processes for transport and buffer layers benefit from existing supply chains developed for the display and semiconductor industries.
Technical challenges persist in achieving uniform performance across large-area tandem devices. The hygroscopic nature of many perovskite compositions requires careful control of ambient conditions during solution processing, while CVD parameters must be optimized to prevent damage to underlying layers. Advanced in-situ monitoring techniques, such as spectroscopic ellipsometry integrated with CVD systems, enable real-time adjustment of growth conditions. Solution processing innovations like gas quenching and solvent engineering have improved film uniformity on textured surfaces.
The environmental footprint of hybrid-fabricated tandems compares favorably with other high-efficiency photovoltaic technologies. Life cycle assessments indicate that the energy payback time for perovskite-silicon tandems could be under one year, owing to the thin-film nature of the perovskite absorber and the high energy yield. Lead containment strategies using CVD-grown barrier layers have been shown to prevent leaching under standardized testing protocols. Recycling schemes for end-of-life modules are being developed to recover both silicon and perovskite materials.
Ongoing research focuses on pushing efficiency limits while addressing manufacturability constraints. Novel device architectures like three-terminal tandems and mechanically stacked designs offer alternative pathways that relax current-matching requirements. Advanced light management schemes combining solution-processed scattering layers with CVD-grown photonic crystals aim to surpass 35% efficiency. The integration of machine learning for process optimization is accelerating the development of robust fabrication protocols for both CVD and solution processing steps.
The hybrid approach demonstrates how complementary deposition techniques can overcome limitations inherent to either method alone. By combining the precision of vapor-phase growth with the versatility of solution processing, researchers have unlocked new possibilities for high-performance tandem photovoltaics. Continued progress in interfacial engineering and scalable manufacturing will determine the timeline for commercial deployment of perovskite-silicon tandems in global energy markets.