In this paper we extend work previously undertaken in industries such as semiconductor and flat panel displays to investigate knowledge flows from advanced countries (US, Japan and Europe) to catch-up follower countries (Taiwan, Korea and China), this time in the emergent solar photovoltaic industry. The solar photovoltaic industry is of particular interest in that it is poised between exploitation of first generation (crystalline silicon tech. In this paper we extend work previously undertaken in industries such as semiconductor and flat panel displays to investigate knowledge flows from advanced countries (US, Japan and Europe) to catch-up follower countries (Taiwan, Korea and China), this time in the emergent solar photovoltaic industry. The solar photovoltaic industry is of particular interest in that it is poised between exploitation of first generation (crystalline silicon technologies) and new thin film and organic compound technologies, thus providing distinct sources of knowledge flow as measured by patent citations and linkage. For this study, we deploy a new database of 19,105 solar photovoltaic patents taken out by Taiwan, Korea and China at the USPTO over the 24 years 1984–2008, and analyse the knowledge flows revealed in these patents using a set of 12 International Patent Classification technology categories that we constructed. We demonstrate commonalities in patterns of knowledge flow between solar photovoltaic and earlier industries, but also suggestive differences, such as rising dependence of the catch-up countries on their own intra-national knowledge generation and flow, indicating their shift from imitation to innovation.••Knowledge flowPatent citationSolar photovoltaic (PV)East AsiaImitation to innovationCatch-upThe catch-up strategies used by industrial latecomers are increasingly the subject of scholarly analysis. In addition to studies of production activities and process innovations that have been accomplished, as well as of investment strategies in dominant technologies, it is of great interest to understand the knowledge flows involved, taking patent data as proxy for the flow of knowledge. Since the pathbreaking study of Hu and Jaffe (2003), a rich stream of literature has grown examining knowledge flows from the advanced countries (US, Japan and European countries such as Germany) to latecomer catch-up countries (Taiwan, Korea and now China). This literature, informed by studies of the semiconductor industry (Lee and Wang, 2010, Lee and Yoon, 2010), flat panel displays (FPD) (Hu, 2008, Jang et al., 2009) and mobile communications (Lee and Jin, 2010), has established a number of 'stylized facts' regarding the catch-up process and its dependence on countries securing access to knowledge sources in the advanced countries, as pre-requisite for the launch of assaults on the industries themselves. The key question in such results is the rate at which a latecomer country is able to switch from external knowledge flows to internal knowledge generation (or building of absorptive capacity) – as reflected in citations of external patents compared with internal citations – and the influence on this process of the industrial dynamics involved. The research question guiding this study is to explore the extent to which patterns established in earli. With the awareness of global warming and the rise of fossil fuel energy prices since the late 1990s, the patenting rate concerning green technologies surged in the 2000s (Bauer and Neuhaus, 2008, Glachant et al., 2009). Solar PV is one of the rapid growth alternative-energy technologies to be adopted (Mowery et al., 2010). As reported by Chatham House, the patenting rate of the solar PV technology has risen from less than 200 patents per year prior to 1998 to more than 1400 patents per year in 2007.2 The significant growth of the global solar PV patenting activity during the period 1999–2008 can plausibly be ascribed to the strong demand in the global market.3 Compared to the average 60% growth rate in all industries, the growth rate of patenting activity in the solar PV technology increased by more than 400% from 1999 (around 1800 patents) to 2008 (around 7900). In the country-level comparison, Tseng et al. (2010) suggested that Japan is leading in the a-Si thin film solar PV technology, followed by the US, Germany, Australia, and UK.Hu and Jaffe (2003) initiated a new line of work examining patterns of knowledge diffusion from advanced countries to latecomer catch-up countries with their study of USPTO patents taken out by Korea and Taiwan over the 22-year period from 1977 to 1999. Four stylized facts emerged from their work which have formed a benchmark for subsequent studies of knowledge diffusio. There are many measures of international knowledge flow, in particular, citations in patent documents record knowledge flows between and amongst different geographical areas, and have been widely used by NBER scholars (e.g. Jaffe et al., 1993, Jaffe and Trajtenberg, 1996, Jaffe and Trajtenberg, 1999). This study extends and advances this work, aimi.
