The use of solution processes-as opposed to conventional vacuum processes and vapour-phase deposition-for the fabrication of electronic devices has received considerable attention for a wide range of applications, with a view to reducing processing costs. In particular, the ability to print semiconductor devices using liquid-phase materials could prove essential for some envisaged applications, such as large-area flexible displays. Recent research in this area has largely been focused on organic semiconductors, some of which have mobilities comparable to that of amorphous silicon (a-Si); but issues of reliability remain. Solution processing of metal chalcogenide semiconductors to fabricate stable and high-performance transistors has also been reported. This class of materials is being explored as a possible substitute for silicon, given the complex and expensive manufacturing processes required to fabricate devices from the latter. However, if high-quality silicon films could be prepared by a solution process, this situation might change drastically. Here we demonstrate the solution processing of silicon thin-film transistors (TFTs) using a silane-based liquid precursor. Using this precursor, we have prepared polycrystalline silicon (poly-Si) films by both spin-coating and ink-jet printing, from which we fabricate TFTs with mobilities of 108 cm2 V(-1) s(-1) and 6.5 cm2 V(-1) s(-1), respectively. Although the processing conditions have yet to be optimized, these mobilities are already greater than those that have been achieved in solution-processed organic TFTs, and they exceed those of a-Si TFTs (< or = 1 cm2 V(-1) s(-1)).

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An inexpensive oxide heterojunction solar cell, consisting of a transparent conducting ZnO thin film deposited on a Cu2O sheet prepared by oxidizing copper at a high temperature, has been demonstrated. High-energy conversion efficiencies over 1% were obtained in Al-doped ZnO (AZO)/Cu2O devices fabricated using AZO thin films prepared by pulsed laser deposition (PLD) or r.f. magnetron sputtering. An open-circuit voltage of 0.41 V, a short-circuit current density of 7.13 mA/cm2, a fill factor of 0.42 and an energy conversion efficiency of 1.21% were obtained in a PLD-AZO/Cu2O device under AM2 solar illumination. The high efficiency of AZO/Cu2O devices is attributed to Cu2O sheets with excellent crystallinity and the low damage resulting from AZO depositions at low temperature.