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Hybrid organic-silicon heterojunction solar cells promise a significant reduction on fabrication costs by avoiding energy-intensive processes. However, their scalability remains challenging without a low-cost transparent electrode. In this work, we present solution-processed silver-nanowire meshes that uniformly cover the microtextured surface of hybrid heterojunction solar cells to enable efficient carrier collection for large device area. We systematically compare the characteristics and device performance with long and short nanowires with an average length/diameter of 30 μm/115 nm and 15 μm/45 nm, respectively, to those with silver metal grids. A remarkable power conversion efficiency of 10.1% is achieved with a device area of 1 × 1 cm(2) under 100 mW/cm(2) of AM1.5G illumination for the hybrid solar cells employing long wires, which represents an enhancement factor of up to 36.5% compared to the metal grid counterpart. The high-quality nanowire network displays an excellent spatial uniformity of photocurrent generation via distributed nanowire meshes and low dependence on efficient charge transport under a high light-injection condition with increased device area. The capability of silver nanowires as flexible transparent electrodes presents a great opportunity to accelerate the mass deployment of high-efficiency hybrid silicon photovoltaics via simple and rapid soluble processes.

Interface carrier recombination currently hinders the performance of hybrid organic-silicon heterojunction solar cells for high-efficiency low-cost photovoltaics. Here, we introduce an intermediate 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) layer into hybrid heterojunction solar cells based on silicon nanowires (SiNWs) and conjugate polymer poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS). The highest power conversion efficiency reaches a record 13.01%, which is largely ascribed to the modified organic surface morphology and suppressed saturation current that boost the open-circuit voltage and fill factor. We show that the insertion of TAPC increases the minority carrier lifetime because of an energy offset at the heterojunction interface. Furthermore, X-ray photoemission spectroscopy reveals that TAPC can effectively block the strong oxidation reaction occurring between PEDOT:PSS and silicon, which improves the device characteristics and assurances for reliability. These learnings point toward future directions for versatile interface engineering techniques for the attainment of highly efficient hybrid photovoltaics.

We propose a series-connected hybrid tandem solar cell which consists of an organic solar cell (P3HT/PCBM) as the top cell and an organic/crystalline silicon hybrid solar cell (PEDOT:PSS/c-Si nanowires) as the bottom cell. Based on the device structure, the organic materials can be directly spun-cast onto the inorganic silicon substrate with thermally evaporated metal contacts, making solution-based processes possible for rapid and low-cost production. With a proper design, the hybrid device architecture can achieve a high open-circuit voltage and junction-matched photocurrent, offering a promising approach for next-generation high-efficiency photovoltaics. In this work, we established a device model to investigate the photovoltaic characteristics of the proposed hybrid tandem solar cells by combining the organic and hybrid silicon solar cells with a hypothetic recombination layer (RL). First, the model of single junction solar cells is fitted to the current-voltage curve of fabricated devices. Next, we investigate the properties of the RL between the sub-cells and observe strong correlations with the photovoltaic performance of tandem cells. In our preliminary model, we have realized a cell with an open-circuit voltage (Voc), short-circuit current (Jsc), fill-factor (FF) and power conversion efficiency (PCE) of 1.093 V, 9.715 mA/cm2, 43.725 % and 4.644 %, respectively. We will further tailor the properties of the RL, the active-layer thickness of sub-cells, as well as the band alignment, in order to achieve practical device designs. Currently, the characteristics of real hybrid tandem solar cells remain significantly lower than the simulation result. The reason of such limited cell performance is the poor interfacial contact, which makes it difficult to provide efficient recombination and transport for electrons and holes generated from sub-cells. A number of challenging issues, including interface physics and device design will be discussed.

Hybrid organic-inorganic heterojunction solar cells based on silicon nanowires (SiNWs) are promising candidates for next-generation photovoltaics owing to potentials for low fabrication cost and high efficiency. The SiNW array, fabricated by a simple metal-assisted wet chemical etching method, produces a large surface-area-to-volume ratio, hence allowing efficient light harvesting and charge collection via the formation of a core-sheath p-n junction. However, previously reported power conversion efficiencies (PCEs) are approximately capped at 10%, which is largely depicted by the interface defect densities that limit the open-circuit voltage (Voc) and fill factor (FF). In this work, we introduce a solution-processed, intermediate 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) layer to mitigate the interface recombination loss for hybrid heterojunction solar cells consisted of SiNWs and conjugate polymer poly(3,4-ethylenedioxy-thiophene): poly(styrenesulfonate) (PEDOT:PSS). A record PCE of 11.0% is achieved in contrast to 9.6% from a reference counterpart without TAPC, which represents an enhancement factor of 14.2% ascribed to noticeable improvement in the Voc and FF. The result is further supported by examining indicators for the interface quality via a suppressed dark saturation current and an enhanced minority carrier lifetime which exhibits an increase from 84 μsec without TAPC to 87 μsec with TAPC.

Hybrid solar cells combining organic polymers and inorganic semiconductors are extensively investigated recently due to relatively inexpensive cost and simple fabrication processes. In this work, we demonstrate organic/inorganic hybrid heterojunction solar cells based on gallium arsenide (GaAs) substrate and conjugated polymer poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS). First we performed a one-dimensional device simulation based on a self-consistent Poisson and drift-diffusion solver to survey the band alignment between the conductive polymer and GaAs materials and achieve a practical device design. Second, for device fabrication, we prepare a cleaned one-side-polished planar GaAs wafer, followed by thermal evaporation of back-side metal using either Aluminum or titanium/gold as the cathode. Next, PEDOT:PSS is spun-cast onto the wafer and annealed at 115°C for 10 minutes. To improve carrier conduction, we use a self-assembled polystyrene (PS) nanosphere lithography technique to form the sacrificial mask layer, and perform anisotropic metal-assisted chemical etching on GaAs substrates. Various nanostructures such as nanowires or nanorods allow the conformal p-n heterojunction formation at the interface of organic/inorganic semiconductors, which can be beneficial for both light absorption and carrier collection. The optical and electrical characteristics such as reflectance, current voltage, and external quantum efficiency are measured. Currently, we achieve a 3.2% power conversion efficiency with an open-circuit voltage of 0.565 V, short-circuit current of 8.95 mA/cm2, and a fill factor of 63.29% under a simulated AM1.5G illumination for planar substrates. Device fabrication with GaAs nanowires is still in process and more data will be presented.

Mono- and multi-crystalline silicon photovoltaics currently still hold more than 80% market share because of the non-toxic, abundant material resources used, and their long-term stabilities. However, the cost of solar power is still more than three times that of fossil fuels, which necessitates a further reduction to accelerate its widespread use. It has been estimated that cell fabrication consumes 30% of the total manufacturing cost due to energy intensive semiconductor processes, such as high temperature furnace for doping, electrodes co-firing, high-vacuum chemical deposition, etc. Therefore, the organic-inorganic hybrid cell concept has been proposed to take advantage of the solution-based processes for rapid and low-cost production and the wide absorption spectrum of silicon. In this work, we demonstrate a hybrid heterojunction solar cell based on the structure of conductive polymer PEDOT:PSS spun cast on n-type crystalline silicon nanorod (SiNR) arrays with periodic arrangements. The nanorod arrays are fabricated by electron beam (E-beam) lithography followed by reactive-ion etching (RIE), which show capability to enhance light harvesting. In addition, SiNRs and PEDOT:PSS can form core-shell structure that provides a large p-n junction area for carrier separation and collection. We measured the optical and photovoltaic characteristics of these devices under a simulated class A solar simulator with a calibrated illumination intensity of 1000 W/m2 for the AM1.5G solar spectrum. A post-RIE damage removal etching (DRE) is subsequently introduced in order to mitigate the surface recombination issues and also alter the surface reflection due to modifications in the nanorod side-wall profile. Finally, we show that the DRE treatment can effectively recover the carrier lifetime and dark current-voltage characteristics of SiNRs hybrid solar cells to resemble the planar counterpart without RIE damages.

In this paper, hybrid heterojunction solar cells are demonstrated based on a highly conductive polymer PEDOT:PSS directly spun-cast on an n-type crystalline silicon with microscale surface textures. The fabrication conditions suggest that the organic coverage on the micro-textured surface is excellent and key to achieve high efficiency. The simple solution-based fabrication processes achieved a cell power conversion efficiency of 10.2%. Device modeling had been performed to investigate the interface defect density dependence of cell performances. A power conversion efficiency of above 20% is projected for the hybrid heterojunction cells, showing promises for low-cost photovoltaics.